Synthesis, characterization and application of magnetic biochar sulfonic acid as a highly efficient recyclable catalyst for preparation of spiro-pyrazolo[3,4-b]pyridines

Greener design and characterization of biochar/Fe3O4@SiO2-Ag magnetic nanocomposite as efficient catalyst for synthesis of bioactive benzylpyrazolyl coumarin derivatives

The study aimed to develop an efficient catalyst, biochar/Fe₃O₄@SiO₂-Ag magnetic nanocomposite, to synthesize bioactive benzylpyrazolyl coumarin derivatives through a one-pot multicomponent reaction. The catalyst was prepared using Ag nanoparticles synthesized with Lawsonia inermis leaf extract and carbon-based biochar obtained through pyrolysis of Eucalyptus globulus bark. The nanocomposite contained a silica-based interlayer, highly dispersed Ag nanoparticles, and a central magnetite core, which responded well to external fields. The biochar/Fe₃O₄@SiO₂-Ag nanocomposite showed excellent catalytic activity and could be easily recovered using an external magnet and reused five times without significant loss of performance. The resulting products were tested for antimicrobial activity and showed significant activity against various microorganisms.